The present invention relates to a method of and a system for controlling a hydraulic shock absorber, and more particularly to a damping force control for a shock absorber of the type wherein a flow of damping fluid induces a load on an actuator during bounding and rebounding of the shock absorber.
A shock absorber of the above mentioned type is used in a known vehicle suspension system disclosed by Japanese Utility Model Application First (unexamined) Publication No. 63-112914. The shock absorber comprises an outer cylinder tube, an inner cylinder tube filled with a damping fluid, a piston slidably disposed in the inner cylinder tube to divide the interior of the inner cylinder tube into a first chamber and a second chamber, and a variable flow restrictor for providing a restricted flow of damping fluid between the first and second chambers during bounding and rebounding of the shock absorber. In order to vary flow area of the flow restrictor passage, a rotary valve is operatively connected to an actuator in the form of a stepper motor operative under the control of a control unit. During bounding and rebounding of the shock absorber, there occurs a flow of damping fluid passing through the restricted flow passage, inducing a load on the rotary valve in such a direction as to increase the opening degree of the restricted flow passage. The load on the rotary valve is applied to the actuator, and variable with a pressure generated by the flow of damping fluid passing through the restricted flow passage. However, the magnitude of an output signal of the control unit remains constant for each of range positions which the shock absorber may be conditioned to operate. Thus, the actuator is not controlled in such a manner as to compensate for a change in load applied to the actuator owing to a flow of damping fluid passing through a restricted flow passage.
Accordingly, an object of the present invention is to provide a method of and a system for controlling a hydraulic shock absorber wherein an actuator is controlled in such a manner as to compensate for a change in load induced by a flow of damping fluid passing through a restricted flow passage during bounding and rebounding of the shock absorber.